[PATCH] BC: resource beancounters (v3)

[Kirill Korotaev]

The following patch set presents base of
Resource Beancounters (BC).
BC allows to account and control consumption
of kernel resources used by group of processes.

Draft UBC description on OpenVZ wiki can be found at
http://wiki.openvz.org/UBC_parameters

The full BC patch set allows to control:
- kernel memory. All the kernel objects allocatable
on user demand should be accounted and limited
for DoS protection.
E.g. page tables, task structs, vmas etc.

- virtual memory pages. BCs allow to
limit a container to some amount of memory and
introduces 2-level OOM killer taking into account
container's consumption.
pages shared between containers are correctly
charged as fractions (tunable).

- network buffers. These includes TCP/IP rcv/snd
buffers, dgram snd buffers, unix, netlinks and
other buffers.

- minor resources accounted/limited by number:
tasks, files, flocks, ptys, siginfo, pinned dcache
mem, sockets, iptentries (for containers with
virtualized networking)

As the first step we want to propose for discussion
the most complicated parts of resource management:
kernel memory and virtual memory.
The patch set to be sent provides core for BC and
management of kernel memory only. Virtual memory
management will be sent in a couple of days.

The patches in these series are:
diff-atomic-dec-and-lock-irqsave.patch
 introduce atomic_dec_and_lock_irqsave()

diff-bc-kconfig.patch:
 Adds kernel/bc/Kconfig file with UBC options and
 includes it into arch Kconfigs

diff-bc-core.patch:
 Contains core functionality and interfaces of BC:
 find/create beancounter, initialization,
 charge/uncharge of resource, core objects' declarations.

diff-bc-task.patch:
 Contains code responsible for setting BC on task,
 it's inheriting and setting host context in interrupts.

 Task contains three beancounters:
 1. exec_bc  - current context. all resources are charged
               to this beancounter.
 2. fork_bc  - beancounter which is inherited by
               task's children on fork

diff-bc-syscalls.patch:
 Patch adds system calls for BC management:
 1. sys_get_bcid    - get current BC id
 2. sys_set_bcid    - changes exec_ and fork_ BCs on current
 3. sys_set_bclimit - set limits for resources consumtions
 4. sys_get_bcstat  - returns limits/usages/fails for BC

diff-bc-kmem-core.patch:
 Introduces BC_KMEMSIZE resource which accounts kernel
 objects allocated by task's request.

 Objects are accounted via struct page and slab objects.
 For the latter ones each slab contains a set of pointers
 corresponding object is charged to.

 Allocation charge rules:
 1. Pages - if allocation is performed with __GFP_BC flag - page
    is charged to current's exec_bc.
 2. Slabs - kmem_cache may be created with SLAB_BC flag - in this
    case each allocation is charged. Caches used by kmalloc are
    created with SLAB_BC | SLAB_BC_NOCHARGE flags. In this case
    only __GFP_BC allocations are charged.

diff-bc-kmem-charge.patch:
 Adds SLAB_BC and __GFP_BC flags in appropriate places
 to cause charging/limiting of specified resources.

Summary of changes from v2 patch set:

* introduced atomic_dec_and_lock_irqsave()
* bc_adjust_held_minmax comment
* added __must_check for bc_*charge* funcs
* use hash_long() instead of own one
* bc/Kconfig is sourced from init/Kconfig now
* introduced bcid_t type with comment from Alan Cox
* check for barrier <= limit in sys_set_bclimit()
* removed (bc == NULL) checks
* replaced memcpy in beancounter_findcrate with assignment
* moved check 'if (mask & BC_ALLOC)' out of the lock
* removed unnecessary memset()

Summary of changes from v1 patch set:

* CONFIG_BEANCOUNTERS is 'n' by default
* fixed Kconfig includes in arches
* removed hierarchical beancounters to simplify first patchset
* removed unused 'private' pointer
* removed unused EXPORTS
* MAXVALUE redeclared as LONG_MAX
* beancounter_findcreate clarification
* renamed UBC -> BC, ub -> bc etc.
* moved BC inheritance into copy_process
* introduced reset_exec_bc() with proposed BUG_ON
* removed task_bc beancounter (not used yet, for numproc)
* fixed syscalls for sparc
* added sys_get_bcstat(): return info that was in /proc
* cond_syscall instead of #ifdefs

Many thanks to Oleg Nesterov, Alan Cox, Matt Helsley and others
for patch review and comments.

Patch set is applicable to 2.6.18-rc4-mm3

Thanks,
Kirill
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